The Norris Trophy is awarded every year to the defenseman who "demonstrates throughout the season the greatest all-around ability in the position", but how can you truly separate a defenseman from his regular partner? The model adopted by the William Jennings trophy, which is handed out to both goalies despite the fact that you truly can separate their performances, is the one I prefer.

But which defensive pairing was last year's best, and how can that be determined?

The Top Pairings

Below is the even-strength Player Usage Chart for all of last year's top pairing defensemen, which are defined as whichever two defensemen faced the toughest average competition. Unfortunately those two selected defensemen didn't necessarily always play together, but in most cases they did.

While it's not completely appropriate to compare players across teams like this, and while these shot-based metrics aren't the be-all end-all measurement of how well these players performed, they still give us an approximate idea of how the top pairings were used from one team to another, and how much success each team enjoyed relative to another.

The Stand-outs

The toughest job in hockey went to two pairings: Dan Girardi and Ryan McDonagh in New York, and Chris Butler and Jay Bouwmeester in Calgary, but with very different results. Both teams, either by design or necessity, relied more heavily on their top pairing than on their other defensemen, one of whom was someone who had never before even played in a top-four role (seeif you can guess who!). The results practically speak for themselves, and the Rangers finished tied for 2nd overall and the Flames missed the play-offs.

Of course, having the most difficult assignment doesn't necessarily make someone the best, but if Girardi and McDonagh aren't the league's top pairing, who is? An obvious candidate is Nashville's Shea Weber and Ryan Suter who had a combined 95 points to Girardi/McDonagh's 61, and some of the best possession numbers anywhere in the chart.

Another possibility for league's best top pairing are the nearby big blue possession circles acting as home to Fedor Tyutin and Nikita Nikitin of Columbus. Columbus? That's right, not everything was a disaster in Columbus last year, as they clearly found an unexpectedly effective top pairing.

No discussion of the best top pairings would be complete without considering Nicklas Lidstrom and whoever wins the linemate lottery, which was Ian White in last year's case. With the exception of Nashville there's clearly a pattern of one elite defensemen playing alongside more of a "depth" partner. Playing in Detroit they had the advantage of starting in the offensive zone far more often than anyone else, and they used that end with a combined 66 points and a +44. Yowch!

Speaking of advantages, there's also Tobias Enstrom and Dustin Byfuglien in Winnipeg, who managed 85 points, almost as much as Weber and Suter - although the Jets spread out the defensive responsibilities a little more evenly than any other team, resulting in the easiest top pairing assignment in the league (with the possible exception of Ottawa's superstar Erik Karlsson).

The Strugglers and Surprises

On the flip side, the pairing that might have struggled most is Colorado's Ryan O'Byrne and Jan Hejda. Though the Avalanche, like Winnipeg, spread out the match-ups fairly evenly among their defensemen, their two stay-at-home defensemen were kept almost exclusively in their own zone and got absolutely hammered.

Another surprise disappointment was celebrated and high-priced duo Brooks Orpik and Zbynek Michalek in Pittsburgh. Despite playing on a monster team and being assigned duties certainly no more difficult than any other top pairing they lost the possession game. And though they didn't always play together, the Washington Capitals leaned on their young defensemen John Carlson and Karl Alzner a little harder than the average team, but often found themselves on the losing end possession-wise.

In some cases the team really struggled with one of their top defensemen, like Buffalo's Robyn Regehr or Rostislav Klesla in Phoenix, but did fine with the other, like Andrej Sekera and Oliver Ekman-Larsson in this case. Since you can't really see Sekera and Ekman-Larsson's spot in the big bunching above, here's a break-out graph that shows that one section a little better.

Though you still can't differentiate St. Louis' Carlo Colaiacovo from New Jersey's Mark Fayne, this shows you a bit more detail about these players.

For example, Vancouver's Dan Hamhuis and Kevin Bieksa combined for 81 points and a +41 as a good marker of what a top pairing should look like. As for Edmonton they were enjoying such surprisingly promising results with Ladislav Smid and Jeff Petry that they felt comfortable enough trading Tom Gilbert somewhere where he could work the top line, which probably isn't saying much when you realize we're talking about Minnesota.

Free Agents

Not many of these defensemen are available July 1st, perhaps just Nicklas Lidstrom, Ryan Suter, Bryan Allen, Carlo Colaiacovo, Sheldon Souray, Mike Weaver and Jay Garrison are available.

The Panthers might be wise to let Weaver go, or demote him to an easier assignment, and keep Jay Garrison to continue playing alongside Brian Campbell. If Lidstrom plays another year it'll likely be in Detroit, otherwise Detroit will be in the Suter sweepstakes making it that much more difficult for other teams to upgrade their top pairing.

If Dallas can gamble on Sheldon Souray and win, then there could be potential elsewhere for those looking to improve their top pairing. If a team already has one solid blue liner then they can clearly be paired with a lesser option and remain highly effective. Otherwise, if a team is looking for that solid top gun, sometimes they can find them somewhere among the remaining top-four defensemen, at whom we'll take a closer look next time.

Final Word

The Rangers success came in part from their top pairing of Dan Girardi and Ryan McDonagh handling the league's toughest job far better than a comparable pairing like Calgary's Jay Bouwmeester and Chris Butler. You could make a case for them standing shoulder to shoulder with the league's best top pairings: Shea Weber and Ryan Suter in Nashville, Nicklas Lidstrom and Ian White in Detroit and, strangely enough, Fedor Tyutin and Nikita Nikitin in Columbus.

While other top pairings were equally effective, like Winnipeg's Dustin Byfuglien and Tobias Enstrom and Vancouver's Dan Hamhuis and Kevin Bieksa, none of them were leaned on quite as heavily as those four top pairings, two of which may be split up come July 1st.

As for those who struggled, Colorado may want to re-visit the idea of assigning the toughest minutes to Ryan O'Byrne and Jan Hejda, Pittsburgh should fix whatever was wrong with Brooks Orpik and Zbynek Michalek, and Washington can hopefully continue to develop John Carlson and Karl Alzner a little more carefully.

As for every other team, there are obviously ways to improve top pairings. In many cases they featured a strong talent, some of which were taken off the scrap heap, paired with someone you'd least expect to succeed in a top line role. Next time we'll look at the remaining top-four defensemen and see if we can find some promising candidates.

Rob Vollman of www.HockeyAbstract.com is a regular feature writer on ESPN Insider, co-author of Hockey Prospectus 2010-11 and 2011-12, and regular contributor to NHL Numbers, Flames Nation and Arctic Ice Hockey. Innovator of Player Usage Charts, Quality Starts, GVS (Goals Versus Salary), the Snepsts Projection System, and known for work in League Equivalencies (NHLE). Twitter: @robvollmanNHL

Terrific article and insight. If Columbus had such a strong top pairing, do you think they should improve markedly if they get a goalie and keep Rick Nash? Jack Johnson as a second pairing D-man is alright, right?